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dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=neeraju@codeaurora.org From: Neeraj Upadhyay To: will@kernel.org, mark.rutland@arm.com, marc.zyngier@arm.com, julien.thierry@arm.com, tglx@linutronix.de Subject: [PATCH] arm64: Explicitly set pstate.ssbs for el0 on kernel entry Date: Tue, 9 Jul 2019 16:52:13 +0530 Message-Id: <1562671333-3563-1-git-send-email-neeraju@codeaurora.org> X-Mailer: git-send-email 1.9.1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190709_042603_480004_38E12E72 X-CRM114-Status: GOOD ( 14.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: parthd@codeaurora.org, gkohli@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, Neeraj Upadhyay , linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org For cpus which do not support pstate.ssbs feature, el0 might not retain spsr.ssbs. This is problematic, if this task migrates to a cpu supporting this feature, thus relying on its state to be correct. On kernel entry, explicitly set spsr.ssbs, so that speculation is enabled for el0, when this task migrates to a cpu supporting ssbs feature. Restoring state at kernel entry ensures that el0 ssbs state is always consistent while we are in el1. As alternatives are applied by boot cpu, at the end of smp init, presence/absence of ssbs feature on boot cpu, is used for deciding, whether the capability is uniformly provided. Signed-off-by: Neeraj Upadhyay --- arch/arm64/kernel/cpu_errata.c | 16 ++++++++++++++++ arch/arm64/kernel/entry.S | 26 +++++++++++++++++++++++++- 2 files changed, 41 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index ca11ff7..c84a56d 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -336,6 +336,22 @@ void __init arm64_enable_wa2_handling(struct alt_instr *alt, *updptr = cpu_to_le32(aarch64_insn_gen_nop()); } +void __init arm64_restore_ssbs_state(struct alt_instr *alt, + __le32 *origptr, __le32 *updptr, + int nr_inst) +{ + BUG_ON(nr_inst != 1); + /* + * Only restore EL0 SSBS state on EL1 entry if cpu does not + * support the capability and capability is present for at + * least one cpu and if the SSBD state allows it to + * be changed. + */ + if (!this_cpu_has_cap(ARM64_SSBS) && cpus_have_cap(ARM64_SSBS) && + arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE) + *updptr = cpu_to_le32(aarch64_insn_gen_nop()); +} + void arm64_set_ssbd_mitigation(bool state) { if (!IS_ENABLED(CONFIG_ARM64_SSBD)) { diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 9cdc459..7e79305 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -143,6 +143,25 @@ alternative_cb_end #endif .endm + // This macro updates spsr. It also corrupts the condition + // codes state. + .macro restore_ssbs_state, saved_spsr, tmp +#ifdef CONFIG_ARM64_SSBD +alternative_cb arm64_restore_ssbs_state + b .L__asm_ssbs_skip\@ +alternative_cb_end + ldr \tmp, [tsk, #TSK_TI_FLAGS] + tbnz \tmp, #TIF_SSBD, .L__asm_ssbs_skip\@ + tst \saved_spsr, #PSR_MODE32_BIT // native task? + b.ne .L__asm_ssbs_compat\@ + orr \saved_spsr, \saved_spsr, #PSR_SSBS_BIT + b .L__asm_ssbs_skip\@ +.L__asm_ssbs_compat\@: + orr \saved_spsr, \saved_spsr, #PSR_AA32_SSBS_BIT +.L__asm_ssbs_skip\@: +#endif + .endm + .macro kernel_entry, el, regsize = 64 .if \regsize == 32 mov w0, w0 // zero upper 32 bits of x0 @@ -182,8 +201,13 @@ alternative_cb_end str x20, [tsk, #TSK_TI_ADDR_LIMIT] /* No need to reset PSTATE.UAO, hardware's already set it to 0 for us */ .endif /* \el == 0 */ - mrs x22, elr_el1 mrs x23, spsr_el1 + + .if \el == 0 + restore_ssbs_state x23, x22 + .endif + + mrs x22, elr_el1 stp lr, x21, [sp, #S_LR] /* -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel